1. 
[syn: union, labor union, trade union, trades union, brotherhood]
The Collaborative International Dictionary of English v.0.48:
trades union \trades" un`ion\, or Trade union \Trade" un`ion\ .
   An organized combination among workmen for the purpose of
   maintaining their rights, privileges, and interests with
   respect to wages, hours of labor, customs, etc.
   [1913 Webster] Trades-unionist
WordNet (r) 3.0 (2006):
trades union
    n 1: an organization of employees formed to bargain with the
         employer; "you have to join the union in order to get a
         job" [syn: union, labor union, trade union, trades
         union, brotherhood]